Rare earth-iron (RE-Fe) based alloys can be magnetically hardened by quenching in a substantially amorphous to very finely crystalline microstructure. This is taught, for example, in U.S. Pat. No. 4,496,395 and U.S. Ser. Nos. 414,936 (filed Sept. 3, 1982) and 544,728 (filed Oct. 26, 1983) all to Croat and assigned to the assignee hereof. USSN No. 520,170 to Lee (filed Aug. 4, 1983) and assigned to the assignee hereof teaches how such alloys can be hot-worked to improve their magnetic properties.
Jet casting or melt-spinning is one method of creating such fine microstructures in RE-Fe based alloys. This method entails ejecting a molten stream of alloy through a small orifice onto a rapidly moving quench surface, such as the perimeter of rotating quench wheel. Such rapid cooling creates a very fine ribbon of material in which the crystals of the principal phase have diameters in the range of from about 20-800 nanometers. In RE-Fe-B magnets, this phase has the nominal composition RE.sub.2 Fe.sub.14 B.sub.1. The phase forms for all rare earths and substantial amounts of other transition metals, such as cobalt, can be substituted for Fe.
While jet casting has proven to be an acceptable way of quenching in a desired microstructure in rare earth-iron boron alloys, it would be desirable to arrive at the same result without the inherent problems of jet casting, particularly the problems associated with handling molten rare earth containing alloys.